libreswan setup

function startVPN() {
cat <<EOF > /etc/ipsec.conf
config setup
  nat_traversal=yes
  protostack=netkey
  oe=off
  virtual_private=%v4:10.0.0.0/8,%v4:172.16.0.0/12,%v4:192.168.0.0/16
  keep_alive=60
conn CONN
  authby=secret
  pfs=no
  auto=add
  keyingtries=3
  dpddelay=30
  dpdtimeout=120
  dpdaction=clear
  rekey=yes
  ikelifetime=8h
  keylife=24h
  type=transport
  left=$LOCAL_IP
  leftsubnet=$LOCAL_SUBNET
  leftnexthop=%defaultroute
  right=$REMOTE_IP
  rightsubnet=$REMOTE_SUBNET
EOF
cat /etc/ipsec.conf
echo
echo

cat <<EOF > /etc/ipsec.secrets
%any $REMOTE_IP : PSK "$SHARED_SECRET"
EOF
cat /etc/ipsec.secrets
echo
echo

cat <<EOF > /etc/xl2tpd/xl2tpd.conf
[global]
listen-addr=$LOCAL_IP

[lac vpn-conn]
lns=$REMOTE_IP
ppp debug=yes
pppoptfile=/etc/ppp/options.l2tpd.conf
length bit=yes
EOF
cat /etc/xl2tpd/xl2tpd.conf
echo
echo

cat <<EOF > /etc/ppp/options.l2tpd.conf
ipcp-accept-local
ipcp-accept-remote
refuse-eap
refuse-chap
refuse-mschap
refuse-pap
require-mschap-v2
noccp
noauth
mtu 1200
mru 1200
nodefaultroute
name $USERNAME
password $PASSWORD
EOF
cat /etc/ppp/options.l2tpd.conf
echo
echo

echo 1 > /proc/sys/net/ipv4/ip_forward
for x in /proc/sys/net/ipv4/conf/*; do
  echo 0 > $x/accept_redirects
  echo 0 > $x/send_redirects
done
systemctl restart iptables
iptables --table nat -A POSTROUTING -j MASQUERADE

mkdir -p /var/run/xl2tpd
touch /var/run/xl2tpd/l2tp-control

systemctl start ipsec
sleep 3

systemctl start xl2tpd
sleep 3

ipsec auto --up CONN
sleep 3

echo "c vpn-conn" > /var/run/xl2tpd/l2tp-control
sleep 3

echo

V_IP=$(ip addr show dev ppp0|grep -oP 'inet\ (\d+\.){3}\d+'|awk '{print $2}'|cut -d'/' -f1)
echo "V_IP: $V_IP"
ip route add $REMOTE_SUBNET via $V_IP dev ppp0
}

function stopVPN() {
echo 'ipsec auto --down CONN'
ipsec auto --down CONN
sleep 3

echo -n 'systemctl stop xl2tpd '
systemctl stop xl2tpd
sleep 3

echo -n 'systemctl stop ipsec '
systemctl stop ipsec
sleep 3

rm -f /etc/ipsec.conf
rm -f /etc/ipsec.secrets
rm -f /etc/xl2tpd/xl2tpd.conf
rm -f /etc/ppp/options.l2tpd.conf
}

USERNAME='your_USERNAME'
PASSWORD='your_PASSWORD'

LOCAL_IP='your_LOCAL_IP'
LOCAL_MASK='your_LOCAL_MASK'
LOCAL_SUBNET='your_LOCAL_SUBNET'

REMOTE_IP='your_REMOTE_IP'
REMOTE_SUBNET='your_REMOTE_SUBNET'
SHARED_SECRET='your_SHARED_SECRET'

stopVPN
startVPN